Need some help with "Present Perfect vs Past Simple"
I had a task, looks like that some time ago: -- Tom ... his hand when he was cooking the dinner --. And there were 3 ways to answer - a) burnt, b) was burning, c) has burnt. And couldn't choose among "A" and "C". So, I know, that we normally use Present Perfect, when the action finished in the past, but we don't know when exactly (or it isn't important) and we have the connnection with now. But there isn't any markers of the time in the task and we can see Past Continuos and this tense can't be finished (because it is continous, xd). So, I'm confused a bit. Can somebody tell me why I have to use this or that response option and explain WHY?